bmp_iter_and_compl (&(ITER), &(BITNUM)); \
bmp_iter_next (&(ITER), &(BITNUM)))
+/* A class that ties the lifetime of a bitmap to its scope. */
+class auto_bitmap
+{
+ public:
+ auto_bitmap () { bits = BITMAP_ALLOC (NULL); }
+ ~auto_bitmap () { BITMAP_FREE (bits); }
+ // Allow calling bitmap functions on our bitmap.
+ operator bitmap () { return bits; }
+
+ private:
+ // Prevent making a copy that references our bitmap.
+ auto_bitmap (const auto_bitmap &);
+ auto_bitmap &operator = (const auto_bitmap &);
+#if __cplusplus >= 201103L
+ auto_bitmap (auto_bitmap &&);
+ auto_bitmap &operator = (auto_bitmap &&);
+#endif
+
+ bitmap bits;
+};
+
#endif /* GCC_BITMAP_H */
return 0;
}
+/* Return TRUE if an SSA_NAME maybe undefined and is therefore
+ unsuitable for unswitching. STMT is the statement we are
+ considering for unswitching and LOOP is the loop it appears in. */
+
+static bool
+is_maybe_undefined (const tree name, gimple *stmt, struct loop *loop)
+{
+ /* The loop header is the only block we can trivially determine that
+ will always be executed. If the comparison is in the loop
+ header, we know it's OK to unswitch on it. */
+ if (gimple_bb (stmt) == loop->header)
+ return false;
+
+ auto_bitmap visited_ssa;
+ auto_vec<tree> worklist;
+ worklist.safe_push (name);
+ bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (name));
+ while (!worklist.is_empty ())
+ {
+ tree t = worklist.pop ();
+
+ /* If it's obviously undefined, avoid further computations. */
+ if (ssa_undefined_value_p (t, true))
+ return true;
+
+ /* A PARM_DECL will not have an SSA_NAME_DEF_STMT. Parameters
+ get their initial value from function entry. */
+ if (SSA_NAME_VAR (t) && TREE_CODE (SSA_NAME_VAR (t)) == PARM_DECL)
+ continue;
+
+ gimple *def = SSA_NAME_DEF_STMT (t);
+
+ /* Check that all the PHI args are fully defined. */
+ if (gphi *phi = dyn_cast <gphi *> (def))
+ {
+ for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
+ {
+ tree t = gimple_phi_arg_def (phi, i);
+ /* If an SSA has already been seen, it may be a loop,
+ but we can continue and ignore this use. Otherwise,
+ add the SSA_NAME to the queue and visit it later. */
+ if (TREE_CODE (t) == SSA_NAME
+ && bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t)))
+ worklist.safe_push (t);
+ }
+ continue;
+ }
+
+ /* Uses in stmts always executed when the region header executes
+ are fine. */
+ if (dominated_by_p (CDI_DOMINATORS, loop->header, gimple_bb (def)))
+ continue;
+
+ /* Handle calls and memory loads conservatively. */
+ if (!is_gimple_assign (def)
+ || (gimple_assign_single_p (def)
+ && gimple_vuse (def)))
+ return true;
+
+ /* Check that any SSA names used to define NAME are also fully
+ defined. */
+ use_operand_p use_p;
+ ssa_op_iter iter;
+ FOR_EACH_SSA_USE_OPERAND (use_p, def, iter, SSA_OP_USE)
+ {
+ tree t = USE_FROM_PTR (use_p);
+ /* If an SSA has already been seen, it may be a loop,
+ but we can continue and ignore this use. Otherwise,
+ add the SSA_NAME to the queue and visit it later. */
+ if (bitmap_set_bit (visited_ssa, SSA_NAME_VERSION (t)))
+ worklist.safe_push (t);
+ }
+ }
+ return false;
+}
+
/* Checks whether we can unswitch LOOP on condition at end of BB -- one of its
basic blocks (for what it means see comments below). */
/* Condition must be invariant. */
FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
{
- /* Unswitching on undefined values would introduce undefined
- behavior that the original program might never exercise. */
- if (ssa_undefined_value_p (use, true))
- return NULL_TREE;
def = SSA_NAME_DEF_STMT (use);
def_bb = gimple_bb (def);
if (def_bb
&& flow_bb_inside_loop_p (loop, def_bb))
return NULL_TREE;
+ /* Unswitching on undefined values would introduce undefined
+ behavior that the original program might never exercise. */
+ if (is_maybe_undefined (use, stmt, loop))
+ return NULL_TREE;
}
cond = build2 (gimple_cond_code (stmt), boolean_type_node,
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